The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Majorana fermions are the condensed matter analogs of elementary spin-½ particles originally proposed by Ettore Majorana. Majorana fermions are characterized, in part, by being their own anti-particles. Because of their unique quantum properties, researchers have known for some time that Majorana fermions can be implemented as a new form of electronic states of matter. And as such, researchers have known that Majorana fermions could have applications for information processing and computing, and in particular in quantum computation and storage.
The idea that a pair of Majorana fermions can be engineered in the laboratory grew from the theoretical observation that proximity induced superconductivity on the surface state of a topological insulator is topological in nature. Research showed that pairing, on a “spin-less” Fermi surface created by the spin-momentum locking of topological surface states, must effectively include a p-wave superconductor to satisfy the pair-wavefunction anti-symmetry requirement to produce a topological superconductor. This approach was later extended to systems in which a semiconductor nanowire, with strong spin orbit interactions in a parallel magnetic field, would be placed in contact with a superconductor.
The semiconductor nanowire system required fine-tuning of various parameters, such as the chemical potential of the system. Further, the semiconductor nanowire system required the application of an external magnetic field to produce the interaction required to produce the Majorana fermions within the nanowire. In turn, the semiconductor nanowire platform is complex and difficult to implement.
Despite the complexity, experimental efforts to create Majorana fermions using the semiconductor nanowire system have uncovered evidence for a zero bias peak (ZBP) in tunneling spectroscopy studies. Theoretically, such a zero bias peak could be a signature of presence of Majorana fermion. However, the ZBPs detected in such devices are believed to be caused by the Kondo effect or disorder, and not therefore indicative of the presence of Majorana fermions. Crucially, in order for the ZBP to be correctly identified as a Majorana fermion, it must appear at the end of the semiconductor nanowire. However, conventional experimental efforts have failed to provide evidence for the presence of Majorana fermions, because the zero bias peaks are not spatial separated.
Without isolation of the Majorana fermions in well-defined regions, creating useful devices, whether qubit devices or otherwise, is still allusive. In fact, without proving spatial isolation of the ZBP, one cannot confirm the presence of Majorana fermions.